JPH05133401A - Flow rate control device - Google Patents

Abstract

PURPOSE:To perform feedback control with high accuracy by correcting a measurement error in a flow sensor due to temperature change. CONSTITUTION:This device is provided with a flow rate control valve 2 which is installed in a working oil passage of a hydraulic actuator 31 and opened/ closed according to a driving signal, a valve driving means 32 which drives the flow rate control valve 2 according to the preset directed flow rate Qr and feedback flow rate Qf, a flow measuring means 33 which measures flow rate Qi of hydraulic oil of the control valve 2, and a displacement sensor 34 which measures displacement of the hydraulic actuator 31. Also, there are provided a time measuring means 35 which measures time DELTAT taken until the output of the displacement sensor 34 has reached a prescribed displacement Lo, a means 38 which calculates target time To taken until the hydraulic actuator 31 has reached the prescribed displacement Lo based on the directed flow rate Qr, a means 36 which corrects the measured flow rate Qi according to the measured time DELTAT and the target time To, and a means 37 which outputs the correction value to the valve driving means 32 as the feedback flow rate Qf.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flow control device for feedback controlling the speed and position of a hydraulic actuator with a flow control valve.

[0002]

2. Description of the Related Art As a device for feedback controlling the speed of a hydraulic actuator by means of a flow control valve, FIG.
As shown in FIG. 1, the valve controller 1 determines the flow rate of the flow control valve 2 from the preset flow rate Q _r and the measured flow rate Q _i measured by the flow meter 3 according to the designated flow rate Q _r and the measured flow rate Q _i . It is known that the opening degree is corrected and the speed of the hydraulic actuator 4 is controlled by performing feedback control so as to match the indicated flow rate Q _r .

[0003]

However, when the temperature or viscosity of the hydraulic oil changes, the actual flow rate changes even with the same valve opening, and the measured flow rate Q _i of the flow meter 3 also changes. However, since the indicated flow rate Q _r does not necessarily match the actual flow rate Q actually flowing into the hydraulic actuator 4, there is a problem that accurate feedback control is not performed.

Therefore, according to the present invention, the measurement error of the flow rate sensor due to the change of the temperature of the hydraulic oil is corrected, and the actual flow rate and the measured flow rate are made to coincide with each other to perform highly accurate feedback control.

[0005]

As shown in FIG. 1, a first invention is a flow control valve 2 which is interposed in a hydraulic oil passage of a hydraulic actuator 31 and opens and closes in accordance with a drive signal, and a preset command flow rate. Valve drive means 32 for driving the flow rate control valve 2 according to Q _r and the feedback flow rate Q _f.
A flow rate measuring means 33 for measuring the flow rate Q _i of the hydraulic oil of the flow rate control valve 2, a displacement sensor 34 for measuring the displacement amount of the hydraulic actuator 31, and the output of this displacement sensor 34 becomes a predetermined displacement amount L ₀ . The time measuring means 35 for measuring the time ΔT until reaching, and the target time T _{0 at} which the hydraulic actuator 31 reaches a predetermined displacement amount L ₀ based on the indicated flow rate Q _r.
Means 38 for calculating, the measured time ΔT and the target time T
A means 36 for correcting the measured flow rate Q _i according to ₀ and a feedback flow rate Q _{f for the} correction value to the valve driving means 32.
And a means 37 for outputting as.

In the second invention, the displacement sensor 34 measures the displacement amount of the hydraulic actuator 31 in a predetermined section L ₀ .

In the third invention, the displacement sensor 34 continuously measures the displacement amount of the hydraulic actuator 31 for each predetermined unit section L ₀ .

According to a fourth aspect of the invention, the correction means 36 corrects the measured flow rate Q _i at the next displacement based on the measurement time ΔT required for the displacement of the hydraulic actuator 31 in the previous predetermined section L ₀ .

In a fifth aspect of the invention, the correction means 36 continuously measures the time required for the displacement of the hydraulic actuator 31 for each predetermined unit section L ₀ , and the measurement time ΔT _{n-1 of the} previous section.
Based on the above, the measured flow rate Q _i in the next section is corrected.

[0010]

In the first aspect of the present invention, the measured flow rate Q _{i is} calculated according to the target time T ₀ calculated from the time ΔT required for the hydraulic actuator 31 to displace the predetermined displacement amount L ₀ and the preset command flow rate Q _r. Is corrected to eliminate an error from the actual flow rate Q actually supplied to the hydraulic actuator 31, a feedback flow rate Q _f is calculated from the corrected measured flow rate Q _i, and feedback control is applied to the valve driving means 32.

In the second aspect of the invention, the displacement sensor 34 measures the displacement amount of the hydraulic actuator 31 in the predetermined section L ₀ , and the time required for this displacement is ΔT.

A third aspect of the present invention, the displacement sensor 34 is a displacement amount for each predetermined unit interval L ₀ continuously measured hydraulic actuator 31, the time required for the displacement of the unit sections L ₀ and [Delta] T.

In a fourth aspect of the invention, the correcting means 36 corrects the measured flow rate Q _i at the next displacement based on the measurement time ΔT required for the displacement of the hydraulic actuator 31 in the previous predetermined section L ₀ and the target time T _0. ..

In a fifth aspect of the invention, the correction means 36 continuously measures the time required for the displacement of the hydraulic actuator 31 in each predetermined unit section L ₀ , and the measurement time ΔT _n-1 and the target time T in the previous section are measured. The measured flow rate Q _{in in the} next section is corrected based on ₀ .

[0015]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 2 shows a first embodiment, 2 is a flow rate control valve for controlling the flow rate of the hydraulic oil supplied from the hydraulic pressure source 21, 3 is installed downstream of the flow rate control valve 2, and A flow meter 4 for measuring the flow rate is a hydraulic cylinder for expanding and contracting the rod 5 according to the supply amount of hydraulic oil.

Numerals 6 and 7 are limit switches provided close to the rod 5, fixed at a predetermined interval L ₀ , and turned on when the tip of the rod 5 passes.

A valve controller 1 opens and closes a flow control valve 2 in accordance with a preset command flow rate Q _r ,
The flow rate is measured from the output signal of the flow meter 3, the time ΔT from when the limit switch 6 is turned on to when the limit switch 7 is turned on is measured, and the measured flow rate Q _i in which the error with respect to the actual flow rate Q is corrected. Feedback control is performed based on.

The contents of this control will first be outlined based on the theory of control, and then the specific control will be described in detail.

Generally, the discharge flow rate for the same opening of the valve changes depending on the working temperature and viscosity of the hydraulic oil, and the detection output of the flow meter 3 for the same flow rate itself depends on the working temperature and viscosity of the hydraulic oil and other disturbances. fluctuate. That is, the measured flow rate Q _i is

[Equation 1]

It is known that the measured value of the measured flow rate Q _i changes with changes in the temperature and viscosity of the hydraulic oil.

When hydraulic oil is supplied to the hydraulic cylinder 4 to extend the rod 5, the rod 5 passes through the limit switch 6 and is turned on, and then the predetermined length L ₀ is moved to turn on the limit switch 7. To do. Assuming that a predetermined time required for displacement of a predetermined displacement amount L ₀ when the rod 5 extends at a predetermined speed with a designated flow rate Q _r is a target time T ₀ , a predetermined displacement amount L ₀ and a valve flow rate Q (hereinafter, actual flow rate). The relation with Q) is expressed by the following equation.

[Equation 2]

The operating speed of the hydraulic cylinder 4 is always the actual flow rate Q.
Therefore, if feedback control is performed when the measured flow rate Q _i and the actual flow rate Q do not match in the above equation, the time required to pass the predetermined displacement amount L ₀ is not T ₀ ,
The difference between the measured flow rate Q _i and the actual flow rate Q can be known from the change in time required for the predetermined displacement amount L ₀ .

The time required to displace the known section L _{0 when} the measured flow rate Q _i ≠ the actual flow rate Q is ΔT, while the indicated flow rate Q _r = measured flow rate Q _i = the actual displacement Q, the time to displace L _0. Is the target time T ₀ , ΔT and T ₀ are different as shown in the following equation.
It should be noted that this L ₀ is calculated based on the indicated flow rate Q _r as in the equation (6) described later.

[Equation 3]

Therefore, as a constant for correcting the error between the measured flow rate Q _{i and} the actual flow rate Q, a correction constant K _C shown in the following equation is calculated.

[Equation 4]

Next, the feedback flow rate Q _f from which the measurement error is eliminated is expressed by the following equation from the measured flow rate Q _i and the correction constant K _C.

[Equation 5]

The valve controller 1 according to the above equation (4).
Since it suffices to open / close the flow rate control valve 2 by adding the feedback flow rate Q _f so that the indicated flow rate Q _r and the actual flow rate Q match, the measured flow rate Q _i can be calculated from the equations (3) and (4). The feedback flow rate Q _f after correction of is determined by the following equation.

[Equation 6]

That is, the feedback flow rate Q obtained by correcting the error between the measured flow rate Q _{i and} the actual flow rate Q by the above equation (5).
By matching the _f the indicated flow rate Q _r, it is possible to match the actual flow rate Q in the indicated flow rate Q _r.

When the target time T ₀ is set to the stroke cross-sectional area S of the hydraulic cylinder 4, T ₀ is obtained from the above equation (2) by the following equation.

[Equation 7]

An example of flow rate control to which the above theory is applied will be described with reference to the flowchart of FIG.

When the valve controller 1 is set to the indicated flow rate Q _r and started, the valve controller 1 opens the flow rate control valve 2 in accordance with the indicated flow rate Q _r to supply hydraulic oil to the hydraulic cylinder 4.

The indicated flow rate Q _r is read and this indicated flow rate Q _r
Based on the above, the target time T ₀ is calculated by the equation (7). (Steps 49, 50)

When the rod 5 extends and the tip passes the limit switch 6, the passing time T ₁ is detected and the time measurement is started (steps 51 and 52), and the output of the flow meter 3 is read (step 51). 53).

When the rod 5 moves a predetermined displacement amount L ₀ , the limit switch 7 is turned on, the time T ₂ is detected in step 54, and the time ΔT required for the displacement of L ₀ is calculated (step 55).

At the preset indicated flow rate Q _r , the rod 5
Is a predetermined target time T ₀ required for the displacement of L ₀ and the calculated time ΔT, a correction constant K _C for correcting the measured flow rate Q _i is calculated by the equation (3), and the feedback flow rate is calculated by the equation (5). Q _f is calculated (steps 56 and 57).

Based on the feedback flow rate Q _f calculated in step 57, the valve controller 1 controls the opening / closing of the flow rate control valve 2 to maintain the commanded flow rate Q _r (steps 58 to 61) and the known flow rate Q _r based on the commanded flow rate Q _r. The error between the measured flow rate Q _i and the actual flow rate Q is monitored from the target time T ₀ of Δt and the ΔT obtained in step 55, and the error of the measured flow rate Q _i is corrected by the correction coefficient K _C to set the feedback flow rate Q _f. When the indicated flow rate Q _r is changed, the cycle of resetting the indicated flow rate Q _r according to the change amount ΔQ of the indicated flow rate Q _r is repeated in steps 59 and 61 to repeat the displacement speed of the rod 5 to a predetermined speed at all times. Keep it.

By repeating the above control cycle,
It is possible to perform highly accurate feedback control without being affected by measurement errors of the flowmeter 3 due to disturbances such as changes in the temperature and viscosity of hydraulic oil and overloads, and to constantly drive the hydraulic cylinder 4 at a predetermined speed. Therefore, it is possible to improve the productivity by eliminating the warm-up operation of the hydraulic equipment, and it is possible to perform the flow rate control with high reliability against aging.

FIG. 4 shows a second embodiment. Instead of the limit switches 6 and 7 of the first embodiment, the stroke range of the hydraulic cylinder 4 is divided into n equal parts at a predetermined interval L ₀ ,
N + 1 digital displacement sensors 8 are provided at predetermined intervals.
Is provided. This digital displacement sensor 8
For example, it is composed of a position detector such as a digital stroke sensor, generates a pulse by the displacement of the tip of the rod 5, sends the pulse to the valve controller 1, and the other configurations and controls are the same as those in the first embodiment. ..

As the rod 5 extends, the digital displacement sensor 8 sequentially generates pulses from n _{1 as} shown in FIG. 5, and each pulse has a predetermined interval L ₀ as in the first embodiment. Every time the section is displaced, the predetermined target time T ₀ for displacing the predetermined interval L ₀ at the indicated flow rate Q _r is compared with the time ΔT _n required for the actual displacement to correct the error in the measured flow rate Q _i. Then, the feedback flow rate Q _f is calculated.

Here, when the tip of the rod 5 passes the n _i digital displacement sensor 8 where n = i, the measurement of ΔT _i is started. At this time, the feedback flow rate Q _fi for controlling the flow rate control valve 2 is calculated in the section of ΔT _i−1 where n = i−1, and any section n.
The feedback flow rate Q _{fn in} is calculated by the following equation based on the equations (4) and (5).

[Equation 8]

Therefore, the time ΔT _n for displacing the predetermined interval L ₀ which is a continuous measurement section is sequentially measured, the correction coefficient K _Cn is calculated for each measurement section, and the measured flow rate Q _in and the actual flow rate Q are calculated.
_{Since the} flow rate control valve 2 is controlled by the feedback flow rate Q _fn that eliminates the error from _n , it becomes possible to displace the rod 5 at a predetermined speed by always matching the actual flow rate Q _n with the commanded flow rate Q _r. The flow rate can be controlled with higher accuracy than in the first embodiment.

FIG. 6 shows a third embodiment. Instead of the digital displacement sensor 8 of the second embodiment, an analog displacement sensor 9 is used to set the stroke range of the hydraulic cylinder 4 at a predetermined interval L ₀ . The amount of displacement is continuously detected by dividing it into n equal parts, and is composed of, for example, a potentiometer. Other configurations and controls are the same as those in the first embodiment.

As shown in FIG. 7, the analog displacement sensor 9 detects displacement as the rod 5 extends, and the valve controller 1 calculates L ₀ , which is a predetermined displacement amount. In the same manner as described above, the rod 5 has the predetermined distance L _0.
Each time each section consisting of is displaced, the predetermined target time T ₀ for displacing the predetermined interval L ₀ at the indicated flow rate Q _r is compared with the time ΔT _n required for the actual displacement, and the measured flow rate Q _in The feedback flow rate Q _f is calculated by correcting the error.

Here, when the tip of the rod 5 passes the position of _i-1 L ₀ where n = i−1, the measurement of ΔT _i is started. At this time, the feedback flow rate Q _fi for controlling the flow rate control valve 2 is calculated in the immediately preceding section ΔT _i−1 , and the feedback flow rate Q _fn in an arbitrary section n is expressed by the equation (8). More demanded.

Therefore, the time ΔT _n for displacing the predetermined interval _n L ₀ which is a continuous measurement section is sequentially measured, the correction coefficient K _Cn is calculated for each measurement section, and the measured flow rate Q _in and the actual flow rate Q _n are calculated. Since the flow rate control valve 2 is controlled by the feedback flow rate Q _fn that eliminates the error between the rod 5 and the actual flow rate Q _n , it is possible to displace the rod 5 at a predetermined speed by always matching the commanded flow rate Q _r. By setting the interval _n L _{0 of 2} to be a small amount of displacement, it is possible to perform flow rate control with higher accuracy than in the second embodiment.

Although an example of measuring the linear displacement by the hydraulic cylinder 4 has been shown in the above embodiment, the same control as in the above embodiment can be performed with a hydraulic actuator, for example, although not shown. When a hydraulic motor is used as the hydraulic actuator and a rotary encoder is used as the displacement sensor, a predetermined rotation angle θ ₀ is used instead of the predetermined length L ₀ of the above-described embodiment, and when the indicated flow rate Q _r The correction constant K _C is calculated from the difference between the target time T ₀ required to rotate θ ₀ and the time ΔT required for the actual displacement,
By performing feedback control with the feedback flow rate Q _f obtained by correcting the measured flow rate Q _i , the command flow rate Q _r and the actual flow rate Q are made to match and the hydraulic actuator is always driven at a predetermined speed, as in the above embodiment. Is possible.

Further, in the above embodiment, the flow meter 3 is provided at the subsequent stage of the flow control valve 2. However, although not shown, the flow control valve 2 is provided with a flow meter to simplify the structure of the hydraulic circuit. You can

That is, the valve differential pressure of the flow rate control valve 2 is detected by the pressure sensor, and the valve opening area is detected by the valve controller 1, whereby the measured flow rate Q _i is obtained by the following equation.

[Equation 9]

By processing the measured flow rate Q _i in the same manner as in the above embodiment, it becomes possible to match the indicated flow rate Q _r and the actual flow rate Q with a simple structure.

[0050]

As described above, according to the present invention, the predetermined target time T ₀ required for the hydraulic actuator to displace the predetermined section L ₀ at the indicated flow rate Q _{r and} the time required for the actual displacement. Measured flow rate Q _i using the correction coefficient K _C from the difference from ΔT
Of the feedback flow rate Q _f
Is set to perform feedback control to the flow control valve, which enables highly accurate flow control without being affected by disturbances such as changes in hydraulic oil temperature and viscosity and overload.
It is possible to drive the hydraulic actuator at a predetermined speed at all times, which makes it possible to improve the productivity by eliminating the warm-up operation of hydraulic equipment, and a highly reliable flow rate control device against changes over time. Can be provided.

[Brief description of drawings]

FIG. 1 is a diagram corresponding to a claim of the present invention.

FIG. 2 is a configuration diagram showing an embodiment of the present invention.

FIG. 3 is a control flowchart.

FIG. 4 is a configuration diagram showing another embodiment.

FIG. 5 is a diagram showing a relationship between an output pulse and time.

FIG. 6 is a configuration diagram showing another embodiment.

FIG. 7 is a diagram showing a relationship between displacement and time.

FIG. 8 is a configuration diagram showing a conventional embodiment.

[Explanation of symbols]

 1 Valve Controller 2 Flow Control Valve 3 Flow Meter 4 Hydraulic Cylinder 6 Limit Switch 7 Limit Switch 31 Hydraulic Actuator 32 Valve Driving Means 33 Flow Measuring Means 34 Displacement Sensor 35 Time Measuring Means 36 Measured Flow Compensating Means 37 Signal Generation Means 38 Target Time Calculation means

Claims (5)

[Claims] 1. A flow control valve interposed in a hydraulic oil passage of a hydraulic actuator to open and close according to a drive signal, and valve drive means for driving the flow control valve according to a preset instruction flow rate and feedback flow rate. Flow rate measuring means for measuring the flow rate of the hydraulic oil of the flow rate control valve,
A displacement sensor that measures the displacement amount of the hydraulic actuator, a time measuring unit that measures the time until the output of the displacement sensor reaches a predetermined displacement amount, and the hydraulic actuator reaches the predetermined displacement amount based on the instructed flow rate. A means for calculating a target time, a means for correcting the measured flow rate according to the measured time and the target time, and means for outputting the correction value to the valve driving means as a feedback flow rate. Flow control device. 2. The displacement sensor measures a displacement amount of a hydraulic actuator in a predetermined section.
The flow control device described. 3. The flow control device according to claim 1, wherein the displacement sensor continuously measures a displacement amount of the hydraulic actuator for each predetermined unit section. 4. The flow rate control device according to claim 2, wherein the correction means corrects the measured flow rate at the next displacement based on the previous measurement time of the hydraulic actuator. 5. The flow rate control device according to claim 3, wherein the correction means corrects the measured flow rate in the next section based on the measurement time in the previous section when the hydraulic actuator has the same displacement.